1. Field of the Invention
The present invention relates generally to a cutting blade and the method for producing cutting blades. More particularly, a blade and a method for producing cutting blades which may be used to face hob spiral bevel, zerol, and hypoid gears, wherein the cutter blade contains a cooling passage to continuously cool the contact surface.
2. Description of Related Art
Spiral bevel, zerol and hypoid gears are well known and widely used throughout the automotive industry in a variety of drivetrain applications. Conventional methods for making each of these gears include face milling and face hobbing, with the two methods producing different gear tooth geometry which must be taken into consideration during the gear design. Gears produced by face milling typically have a tapered tooth depth, with the heel end of the tooth being deeper than the toe end of the tooth but they may also have uniform depth teeth. In contrast, gears produced by face hobbing always exhibit a uniform tooth depth. Face milling is an intermittent indexing process which cuts one tooth at a time and then indexes to the next slot so as to cut the adjacent tooth. This process is repeated until all of the teeth have been cut. Face milling is referred to as a two-axis system since the work, or gear, is required to rotate in a timed relationship with a cradle mechanism used to mount a cutter head assembly. In contrast, face hobbing is a continuous indexing process whereby all of the gear teeth are cut simultaneously. Face hobbing is considered a three-axis process since the rotation of the gear, cradle, and cutter head assembly are all in a timed relationship with one another. Face milling is an older process, with face hobbing becoming more important with the advent of computer numerical controlled machines which allows the user to produce either geometry. Customer requirements, engineering and production requirements are considered when selecting either face milling or face hobbing to produce a gear.
Each of the cutting methods utilizes a plurality of cutting blades which are mounted into slots, being typically four-sided and formed in a face of a cutter head. The cutter head is typically a two-piece construction comprising a first, disk-like member and a second, backing ring member which is concentric with the disk. In a known device, portions of each of the blade-receiving slots are formed in both the disk and the backing ring. The two members are sized such that they mate together in an interference fit and known cooling and heating techniques are utilized to assemble the parts. For instance, the disk may be cooled, so as to shrink or reduce its outer diameter, and the concentric backing ring member may be heated so as to increase its inner diameter. After assembly, the two parts may be welded or bored together. This method of assembling the concentric members of the cutter head is known to cause thermal distortion in the slots which receive the individual cutting blades. The slots typically include a radially inward blade seating surface, parallel sidewalls, and a radially outward surface. Known two-axis face milling, tapered depth style cutter heads are normally trued for variations in the radial location of the blade seating surface. This is typically accomplished using shim stock, known as parallels, or by using a system of adjusting wedges, which correct for discrepancies in radial location of the seating surface as small as {fraction (1/10,000)}th of an inch due to the very high accuracy that is required in manufacturing the aforementioned gears. Either the parallels or the adjusting wedges are positioned between the blade seating surface in the cutter head slots and the individual cutting blades so as to provide a method to correct radial position of the blades. Known face mill cutter heads may also be trued for pressure angle variations in the cutter blades using correction wedges to adjust the blade pressure angle.
During the machining process for metal operations, heat builds up between the contact surface of the metal being machined and the blades. This heat facilitates the rapid breakdown of the blades. In metal working operations, coolant is commonly applied to the contact point or area of the tool and workpiece in order to extend the life of the cutting blades. The coolant prevents overheating by absorbing heat due to the working operation and also lubricates the contact area to reduce friction therefore reducing the amount of heat generated by frictional contact of the tool and workpiece. In stock removing processes, coolant further serves to flush metal chips away from the contact area.
In the tools where a plurality of stock removing surfaces, such as cutting blades, are arranged about the face of a tool body or head, it has been conventional to supply coolant to the contact area by spraying. It is known to provide a spraying coolant from the central attachment screw of a milling tool onto the stock removing surfaces of the tool. It is also well known to spray coolant onto a tool and workpiece via one or more externally arranged coolant hoses having their outlets located near the contact area. In spraying, however, delivery of coolant originates from outside of the contact area and does not always adequately supply the tool and workpiece with sufficient coolant.
The prior art shows a rotary ring cutter having cooling passages located within the cutter to supply coolant to discharge outlets located on or between the workpiece and the ring cutter. Another example of the prior art is a carbide drill shaft that contains helically extending ducts for transporting cooling liquid. However, cutter blades used in the hobbing process lack any such cooling means as provided in the prior art.
The need therefore exists for a hob type cutter blade with the capability of supplying coolant directly to the point of contact of the blade and the workpiece.
There exists a further need to manufacture such a hob type cutter without the addition of a further operation.
It is therefore an advantage of the present invention to provide a cooling passage within a hob type cutter blade. The cooling passage permits the flow of coolant through the cutter blade to the contact surface reducing the heat generation as well as dissipating any heat already produced during the hobbing operation. The cooling passage is sintered into the carbide cutter blade without the addition of separate operation during manufacturing.